package edu.Test;

import java.util.Scanner;

public class test21 {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        int n = scan.nextInt();
        double sum  = 0;
        for (int i = 1; i < n; i++) {
            sum += (double)1/i;
        }
        System.out.println(sum);
    }
}
